Step motor control device and electronic timepiece

ABSTRACT

To more surely detect the presence/absence of the rotation of a step motor with a simple structure. In a first detection period immediately after stopping driving of the motor, transistors turn on, the on/off operation of a transistor is controlled at a given frequency, and a detection signal generated in a resistor is taken out from a terminal. Because a current flows in an opposite direction of an equivalent diode of the transistor, the detection signal in the case where the motor does not rotate is suppressed to a low voltage that is equal to or lower than a threshold value. In a second detection period immediately after lapse of the first detection period, the transistors turn on, the on/off operation of the transistor is controlled at a given frequency, and a detection signal generated in a resistor is taken out from the terminal. In the second detection period, because a current flows in a forward direction of an equivalent diode of the transistor, the detection signal is generated without being limited, and the detection signal of a high and stable voltage is obtained in accordance with the rotation of the motor.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a step motor control device thatrotationally drives a step motor and detects the presence/absence of therotation of the step motor, and an electronic timepiece that uses thestep motor control device.

[0003] 1. Description of the Prior Art

[0004] Up to now, in the electronic timepiece, a step motor is used as amotor that rotationally drives time hands such as an hour hand or aminute hand.

[0005]FIG. 5 is a front view showing a step motor used in the electronictimepiece such as a hour hand or a minute hand up to now (for example,refer to Patent Document 1).

[0006] In FIG. 5, the step motor includes a stator 501 made of amagnetic material, a coil 207 wound around on the stator 501, and abipolar rotor 502 disposed within the stator 501. In the stator 501,there are saturable portions 503, 504 and inner notches 505 and 506 fordetermining a stop position of the rotor 502.

[0007] When a drive pulse of a rectangular wave is supplied to the coil207 to allow a current i to flow in a direction indicated by an arrow inFIG. 5, a magnetic flux develops in the stator 501 in the directionindicated by the arrow. As a result, the saturable portions 503 and 504are first saturated, and thereafter the rotor 502 rotates in thedirection indicated by the arrow (counterclockwise) in FIG. 5 by 180degrees due to the interactions between a magnetic pole developed in thestator 501 and a magnetic pole developed in the rotor 502. Subsequently,a pulse current different in the polarity is alternately allowed to flowin the coil 207, to thereby conduct the same operation as the above androtate the rotor 502 counterclockwise in increments of 180 degrees.

[0008]FIG. 6 is a circuit diagram showing a step motor control devicefor conducting the rotation control of the step motor, which has beenused in the electronic timepiece up to now. The circuit is structuredsuch that a rotation drive circuit and a rotation detecting circuit areintegrated together (for example, refer to Patent Document 1).

[0009] In FIG. 6, p-channel MOS transistors Q1, Q2 and n-channel MOStransistors Q3, Q4 are structural elements of the motor drive circuit,and the coil 207 of the step motor is connected between a sourceconnection point of the transistor Q1 and the transistor Q3 and a sourceconnection point of the transistor Q2 and the transistor Q4.

[0010] On the other hand, a detection resistor 208 connected in serieswith the n-channel MOS transistors Q3 to Q6 and the transistor Q5, adetection resistor connected in series with the transistor Q6, and acomparator 210 are structural elements of the rotation detectingcircuit.

[0011] The gates of the respective transistors Q1 to Q6 are connected toa control circuit 103. A connection point OUT2 of the detection resistor208 and the coil 207 and a connection point OUT1 of the detectionresistor 209 and the coil 207 are connected to an input section of thecomparator 210. Also, the input section of the comparator 210 isinputted with a predetermined threshold voltage Vss.

[0012]FIG. 7 is a timing chart for the case of conducting rotationcontrol and detection control in the step motor control device shown inFIG. 6.

[0013] The operation of the conventional step motor control devicestructured as described above will be described with reference to FIGS.5 to 7. First, when a drive pulse P1 is supplied to an input section Viof the control circuit 103, the transistors Q2 and Q3 become an on-stateunder the control by the control circuit 103. As a result, a currentflows in the coil 207 in a direction indicated by an arrow, and therotor 502 rotates counterclockwise as shown in FIG. 5.

[0014] On the other hand, a non-detection period IT, which is a periodduring which the rotation of the step motor is not detected, is providedfor a given period T7 immediately after the motor drive period, and arotation detection period DT for detecting whether or not the step motorrotates is provided for a given period T8 immediately after thenon-detection period IT.

[0015] In the rotation detection period DT, a rotation detection controlpulse SP1 is supplied to the input section Vi of the control circuit103. The control circuit 103 controls the on/off operation of thetransistor Q4 at a given frequency in a state where the transistors Q3and Q4 turn on in response to the rotation detection control-pulse SP1.

[0016] In this situation, a detection signal V8 is taken out from theconnection point OUT1 of the rotation detection resistor 209 and thecoil 207. The detection signal having a waveform shown in FIG. 7 isobtained as the detection signal V8. In FIG. 7, the detection voltage V8lower than VDD is generated when the rotor 502 vibrates counterclockwisein FIG. 5, and the detection voltage V8 higher than VDD is generatedwhen the rotor 502 vibrates clockwise in FIG. 5.

[0017] In the case where the rotor 502 rotates, the detection signal V8that exceeds a given threshold voltage (Vss in this conventionalexample) is obtained, and a rotation detection signal of a high level isoutputted from the comparator 210. In the case where the rotor 502 doesnot rotate, because the detection signal V8 does not reach the thresholdvoltage, the rotation detection signal Vs of a low level is outputtedfrom the comparator 210. It is possible to detect whether or not thestep motor rotates on the basis of the rotation detection signal Vs.After the rotation detection has been completed, the transistors Q3 andQ4 are maintained in the on-state to brake the step motor.

[0018] In a subsequent motor drive period, a subsequent normal drivepulse P1 is supplied to the input section Vi of the control circuit 103.The control circuit 103 controls the transistors Q1 and Q4 to be on, anda drive current flows in the coil 207 in an opposite direction of theabove drive current (counterclockwise in FIG. 5) to thereby rotate therotor 502 counterclockwise.

[0019] In the rotation detection period at this time, when the rotationdetection control pulse SP1 is supplied to the input section Vi of thecontrol circuit 103, the control circuit 103 controls the transistors Q4and Q5 to be on, and controls the on/off operation of the transistor Q3at a given frequency. In this situation, a detection voltage V is takenout from the connection point OUT2 of the resistor 208 and the coil 207,and a level of the detection voltage V is judged by the comparator 210.In the same manner as the above, in the case where the rotor 502rotates, the rotation detection signal Vs of the high level is outputtedfrom the comparator 210, and in the case where the rotor 502 does notrotate, the rotation detection signal Vs of the low level is outputtedfrom the comparator 210. It is impossible to detect whether or not thestep motor rotates in accordance with the rotation detection signal Vs.After the rotation detection has been completed, the transistors Q3 andQ4 are maintained in the on-state to brake the step motor.

[0020] [Patent Document 1]

[0021] JP 57-18440 B (pages 1 to 2, FIG. 1)

[0022] In the step motor control device structured as described above,after the step motor has been driven by the drive pulse P1, the rotor502 freely vibrates at a position where the rotor 502 should stop as acenter. The free vibration of the rotor 502 is large immediately afterthe supply of the drive pulse P1 is finished, and the rotor 502 vibratesin the same direction as a normal rotation direction (counterclockwisein the above-mentioned conventional example) due to the inertia. In thecase where the rotor 502 vibrates counterclockwise, the current flows ina direction indicated by an arrow in FIG. 6.

[0023] On the other hand, an equivalent circuit of the respectivetransistors Q3 to Q6 is made up of a series circuit comprising a switch804 and a resistor 803, and a diode 801 and a capacitor 802 which areconnected in parallel with the series circuit, respectively, as shown inFIG. 8. The respective transistors Q3 to Q6 are considered as an elementequivalently having diodes in one way.

[0024] Accordingly, even through the step motor does not rotate, becausethe counterclockwise vibration of the rotor 502 is large within a givenperiod immediately after the supply of the drive pulse P1 is finished,the detection voltage V7 that exceeds the threshold voltage Vss may beobtained as shown in FIG. 7. That is, in the detection signal V7 that isobtained in a given period T7 immediately after the supply of the drivepulse P1 is finished, a detection voltage having a large peak value isgenerated in the detection resistor 209 due to the large free vibrationof the rotor 502 and misdetection is caused that the step motor isrotating.

[0025] Up to now, in order to prevent such misdetection, the controlcircuit is structured such that a non-detection period IT having a giventime width T7 is set immediately after the supply of the drive pulse isstopped, thereby preventing detection of the rotation of the step motorin the non-detection period IT. Accordingly, there arises such a problemthat the structure of the control circuit is complicated because of theprovision of the non-detection period IT.

[0026] An object of the present invention is to provide a step motorcontrol device in which it is possible to more surely detect therotation of the step motor with a simple structure without any provisionof the non-detection period IT.

[0027] Another object of the present invention is to provide anelectronic timepiece in which it is possible to more surely detect therotation of the step motor for driving the hour hand with a simplestructure.

SUMMARY OF THE INVENTION

[0028] According to the present invention, there is provided a stepmotor control device including: first and second switch elements whichare connected to each other in series; third and fourth switch elementswhich are connected to each other in series; a coil of a step motorwhich is connected between a node of the first and second switchelements and a node of the third and fourth switch elements; a firstseries circuit including a fifth switch element connected in parallelwith the first switch element and a first detection element; a secondseries circuit including a sixth switch element connected in parallelwith the third switch element and a second detection element; a controlmeans that controls an on/off operation of the first to fourth switchelements in response to a drive pulse to allow a current to flow in thecoil to rotationally drive the step motor, and controls an on/offoperation of the fourth, third, fifth, and sixth switch elements inresponse to a rotation detection control pulse that is suppliedimmediately after the supply of the drive pulse is finished in arotation detection period immediately after the rotation drive of thestep motor in accordance with the drive pulse; and a detecting meansthat detects the presence/absence of the rotation of the step motor onthe basis of a comparison result of a voltage generated between thefirst and second detection elements and the coil with a given thresholdvoltage, the device being characterized in that:

[0029] in the case where the step motor is rotationally driven byturning on the first and fourth switch elements in accordance with thedrive pulse, the control means renders the fourth and fifth switchelements on and controls the on/off operation of the third switchelement at a given frequency in a first given period immediately afterthe supply of the drive pulse is finished, and renders the third switchelement and the sixth switch element on and controls the on/offoperation of the fourth switch element at a given frequency in a secondgiven period after lapse of the first given period;

[0030] in the case where the step motor is rotationally driven byturning the second and third switch elements on in accordance with thedrive pulse, the control means renders the third and sixth switchelements on and controls the on/off operation of the fourth switchelement at a given frequency in the first given period immediately afterthe supply of the drive pulse is finished, and renders the fourth switchelement and the fifth switch element on in the second given period andcontrols the on/off operation of the third switch element at a givenfrequency; and

[0031] the detection means detects the presence/absence of the rotationof the step motor on the basis of the comparison result of the voltagegenerated between the first detection element and the coil with thethreshold voltage when the fifth switch element is turned on, anddetects the presence/absence of the rotation of the step motor on thebasis of the comparison result of the voltage generated between thesecond detection element and the coil with the threshold voltage whenthe sixth switch element is turned on.

[0032] In the case where the step motor is rotationally driven byturning on the first and fourth switch elements in accordance with thedrive pulse, the control means renders the fourth and fifth switchelements on and controls the on/off operation of the third switchelement at a given frequency in a first given period immediately afterthe supply of the drive pulse is finished, and renders the third switchelement and the sixth switch element on and controls the on/offoperation of the fourth switch element at a given frequency in a secondgiven period after lapse of the first given period; and in the casewhere the step motor is rotationally driven by turning the second andthird switch elements on in accordance with the drive pulse, the controlmeans renders the third and sixth switch elements on and controls theon/off operation of the fourth switch element at a given frequency inthe first given period immediately after the supply of the drive pulseis finished, and renders the fourth switch element and the fifth switchelement on and controls the on/off operation of the third switch elementat the given frequency in the second given period. The detection meansdetects the presence/absence of the rotation of the step motor on thebasis of the comparison result of the voltage generated between thefirst detection element and the coil with the threshold voltage when thefifth switch element is in an on state, and the detection means detectsthe presence/absence of the rotation of the step motor on the basis ofthe comparison result of the voltage generated between the seconddetection element and the coil with the threshold voltage when the sixthswitch element is in an on state.

[0033] Here, the first, third, fifth, and sixth switch elements may bemade up of n-channel MOS transistors, and the second and fourth switchelements may be made up-of p-channel MOS transistors.

[0034] Further, the first and second detection elements may be made upof resistors.

[0035] Further, according to the present invention, there is provided anelectronic timepiece including a step motor that rotates time hands anda step motor control device that rotationally controls the step motor,the timepiece being characterized in that any of the step motor controldevice described above is used as the step motor control device.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0036] A preferred form of the-present invention is illustrated in theaccompanying drawings in which:

[0037]FIG. 1 is a block diagram showing an electronic timepiece inaccordance with an embodiment of the present invention;

[0038]FIG. 2 is a circuit diagram for explaining the operation of thestep motor control device in accordance with the embodiment of thepresent invention;

[0039]FIG. 3 is a circuit diagram for explaining the operation of thestep motor control device in accordance with the embodiment of thepresent invention;

[0040]FIG. 4 is a timing chart showing the step motor control device;

[0041]FIG. 5 is a front view showing a general step motor;

[0042]FIG. 6 is a circuit diagram for explaining the operation of aconventional step motor control device;

[0043]FIG. 7 is a timing chart of a conventional step motor controldevice; and

[0044]FIG. 8 is an equivalent circuit diagram of a general n-channel MOStransistor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0045] Hereinafter, an embodiment of the present invention will bedescribed in detail with reference to the accompanying drawings.

[0046]FIG. 1 is a block diagram showing an electronic timepiece using astep motor control device in accordance with an embodiment of thepresent invention, and shows an example of an analog electronicwristwatch.

[0047] Referring to FIG. 1, an oscillating circuit 101 is connected toan input section of a control circuit 103 through a frequency dividingcircuit 102. A first output section of the control circuit 103 isconnected to a step motor 105 for driving a time hand through a motordrive circuit 104. A second output section of the control circuit 103 isconnected to a control input section of a rotation detecting circuit106. The rotation detecting circuit 106 that detects whether or not themotor 105 rotates is connected between the motor 105 and the controlcircuit 103. The rotation detecting circuit 106 structures a rotationdetecting means.

[0048] The step motor 105 is identical in structure with the step motorshown in FIG. 5. Also, the structure per se of the motor drive circuit104 and the rotation detecting circuit 106 are identical with that shownin FIG. 6, but a method of controlling the on/off operation of therespective transistors Q1 to Q6 is different from the conventionalexample shown in FIG. 6 as will be described later.

[0049] The frequency dividing circuit 102 divides a reference clocksignal from the oscillating circuit 101 and outputs the dividedreference clock signal to the control circuit 103. The control circuit103 receives a signal from the frequency dividing circuit 102 andoutputs a drive pulse to the motor drive circuit 104. In the drivepulse, there are prepared a normal drive pulse P1 which is a drive pulseof a given pulse width smaller in an effective energy and a correctiondrive pulse that is a drive pulse of a wide width larger in theeffective energy than the normal drive pulse, and the control circuit103 selectively outputs the normal drive pulse and the correction drivepulse to the motor drive circuit 104 in accordance with a detectionsignal from the rotation detecting circuit 106. In this example, thecontrol circuit 103 structures a drive pulse generating means thatgenerates a drive pulse.

[0050] Also, the control circuit 103 supplies to the rotation detectingcircuit 106 a rotation detection control pulse necessary in executingthe rotation detection of the motor 105. In this example, the controlcircuit 103 structures a rotation detection control pulse generatingmeans that generates the rotation detection control pulse.

[0051] The control circuit 103, the motor drive circuit 104, and therotation detecting circuit 106 structure a control means.

[0052]FIGS. 2 and 3 are explanatory diagrams showing the operation ofthe motor drive circuit 104 and the rotation detecting circuit 106 inthe step motor control device in accordance with an embodiment of thepresent invention, respectively, in which FIG. 2 is an explanatorydiagram showing the operation in a given period T1 immediately after adrive pulse is blocked in a rotation detection period, and FIG. 3 is anexplanatory diagram showing the operation in a given period T2immediately after lapse of the given period T1 in the rotation detectionperiod.

[0053] In FIGS. 2 and 3, p-channel MOS transistors Q1, Q2 and n-channelMOS transistors Q3, Q4 are transistors contained in the motor drivecircuit 104, and a coil 207 of the motor 105 is connected between asource connection point of the transistor Q1 and the transistor Q3 and asource connection point of the transistor Q2 and the transistor Q4.

[0054] N-transistor MOS transistors Q5, Q6, a rotation detectionresistor 208 that is connected in series with the transistor Q5, arotation detection resistor 209 connected in series with the transistorQ6, and a comparator 210 are included in the rotation detecting circuit106.

[0055]FIG. 4 is a timing chart for the step motor control device inaccordance with this embodiment, which is a timing chart for the case ofexecuting the rotation detection of the motor 105 by the rotationdetecting circuit 106 in response to a rotation detection control pulseSP1 after rotating the motor 105 in accordance with the normal drivepulse P1.

[0056] Hereinafter, the operation of the step motor control device andthe electronic timepiece in accordance with the embodiment of thepresent invention will be described with reference to FIGS. 1 to 4properly referring to FIGS. 5 and 8.

[0057] First, in a motor drive period, the normal drive pulse P1 issupplied to the motor drive circuit 104 from the control circuit 103,whereby the motor drive circuit 104 rotationally controls the motor 105.In this case, the transistors Q2 and Q3 of the motor drive circuit 104are controlled to be on, as a result of which a drive current flows inthe coil 207, and the motor 105 rotates counterclockwise (in a directionindicated by an arrow) in a front view of FIG. 5 by 180 degrees.

[0058] In a subsequent motor drive period, when a subsequent normaldrive pulse P1 is supplied to the motor drive circuit 104 from thecontrol circuit 103, the transistors Q1 and Q4 are controlled to be on,a drive current flows in the coil 207 in an opposite direction of thedrive current, and the motor 105 rotates counterclockwise of the samedirection by 180 degrees.

[0059] Thereafter, the above operation is repeated to continuouslyrotate the motor 105 counterclockwise.

[0060] On the other hand, a rotation detection period DT for detectingwhether or not the motor 105 rotates (first rotation detection periodT1+second rotation detection period T2) is provided immediately afterthe respective motor drive periods. It is possible to appropriatelyselect the first and second rotation periods T1 and T2 in accordancewith the structure of the motor at the time of designing the motor. Inthe rotation detection period DT, the rotation detection control pulseSP1 is supplied to the rotation detecting circuit 106 from the controlcircuit 103.

[0061] In the first detection period T1 immediately after the supply ofthe respective drive pulses P1 has been completed (immediately after themotor drive stops), the motor drive circuit 104 and the rotationdetecting circuit 106 controls the transistors Q4 and Q5 to be on inresponse to the rotation detection control pulse SP1 from the controlcircuit 103 as shown in FIG. 2, and controls the on/off operation of thetransistor Q3 at a given frequency in accordance with the respectivefine pulses that structures the rotation detection control pulse SP1 ina state where the transistors Q4 and Q5 are turned on. In this state,the detection signal V1 generated in the rotation detection resistor 208is taken out from the terminal OUT2.

[0062] In the first detection period T1, a loop in a direction of acurrent Ik is structured by the transistor Q5, the detection resistor208, the coil 207, and the transistor Q4. In this case, because thecurrent Ik flows in an opposite direction of an equivalent diode 801(refer to FIG. 8) which structures the transistor Q5, the detectionsignal V1 is suppressed to a low voltage within a given range, andtherefore the detection signal V1 of a high voltage which exceeds agiven threshold value (Vss in this embodiment) is not obtained in thecase where the motor does not rotate. As a result, it is possible tosuppress the misdetection in the case where the motor does not rotatewith a simple structure without setting the non-detection period IT evenimmediately after the supply of the drive pulse P1 is stopped.

[0063] In the case where the voltage of the detection signal V1 changesbeyond the threshold voltage, that is, in the case where the motor 105rotates, the rotation detection signal Vs of the high level whichrepresents that the motor 105 rotates is outputted from the comparator210, and after the transistors Q3 and Q4 turn on and the motor rests,the period is shifted to a subsequent motor drive period.

[0064] On the other hand, in the second detection period T2 providedimmediately after lapse of the first detection period T1, the motordrive circuit 104 and the rotation detecting circuit 106 control thetransistors Q3 and Q6 to be on in accordance with the rotation detectioncontrol pulse SP1 from the control circuit 103 as shown in FIG. 3, andcontrol the on/off operation of the transistor Q4 at a given frequencyin accordance with the respective fine pulses that structure therotation detection control pulse SP1 in a state where the transistors Q3and Q6 are turned on. In this state, the detection signal V2 generatedin the rotation detection resistor 209 is taken out from the terminalOUT1.

[0065] In the second detection period T2, because a current Ik flows ina forward direction of the equivalent diode 801 that structures thetransistor Q6 (refer to FIG. 8), the detection signal V2 is not limited,and therefore there is obtained the detection signal V2 of a stablevoltage responsive to the rotation of the motor.

[0066] In the case where the voltage of the detection signal V2 changesbeyond the threshold value, that is, in the case where the motor 105rotates, the rotation detection signal Vs of the high level whichrepresents that the motor 105 rotates is outputted from the comparator210, and after the transistors Q3 and Q4 turn on and the motor rests,the period is shifted to a subsequent motor drive period.

[0067] In the case where the motor 105 does not rotate, the detectionsignal V2 does not exceed the threshold value over the entire detectionperiod DT, and the rotation detection signal Vs of the low level whichrepresents that the motor 105 is in a non-rotation state is outputted tothe entire detection period DT from the comparator 210. The controlcircuit 103 outputs the correction drive pulse wider in width than thenormal drive pulse P1 to the motor drive circuit 104 in response to therotation detection signal Vs that is representative of non-rotation. Themotor drive circuit 104 rotationally drives the motor 105 in response tothe correction drive pulse.

[0068] In this manner, according to the step motor control device ofthis embodiment, it is possible to suppress a possibility of misjudgingthat the motor is rotated in the case where the motor is not rotatedwith a simple structure without providing the non-detection period IT,and it is possible to more surely detect the rotation of the step motor.

[0069] Also, according to the electronic timepiece of this embodiment,it is possible to more surely detect the rotation of the step motor fordriving the hour hand with a simple structure.

[0070] In this embodiment, an example in which the step motor controldevice is used in the electronic timepiece was described, but it ispossible to use the step motor control device in another electronicdevice.

[0071] According to the present invention, it is possible to more surelydetect the rotation of the step motor with a simple structure withoutany provision of the non-detection period in the step motor controldevice.

[0072] Also, according to the present invention, in the electronictimepiece, it is possible to more surely detect the rotation of the stepmotor for driving the hour hand with a simple structure.

What is claimed is:
 1. A step motor control device comprising: first andsecond switch elements which are connected to each other in series;third and fourth switch elements which are connected to each other inseries; a coil of a step motor which is connected between a node of thefirst and second switch elements and a node of the third and fourthswitch elements; a first series circuit including a fifth switch elementconnected in parallel with the first switch element and a firstdetection element; a second series circuit including a sixth switchelement connected in parallel with the third switch element and a seconddetection element; a control means that controls an on/off operation ofthe first to fourth switch elements in response to a drive pulse toallow a current to flow in the coil to rotationally drive the stepmotor, and controls an on/off operation of the fourth, third, fifth, andsixth switch elements in response to a rotation detection control pulsethat is supplied immediately after the supply of the drive pulse isfinished in a rotation detection period immediately after the rotationdrive of the step motor in accordance with the drive pulse; and adetecting means that detects the presence/absence of the rotation of thestep motor on the basis of a comparison result of a voltage generatedbetween the first and second detection elements and the coil with agiven threshold voltage; wherein in the case where the step motor isrotationally driven by turning on the first and fourth switch elementsin accordance with the drive pulse, the control means renders the fourthand fifth switch elements on and controls the on/off operation of thethird switch element at a given frequency in a first given periodimmediately after the supply of the drive pulse is finished, and rendersthe third switch element and the sixth switch element on and controlsthe on/off operation of the fourth switch element at a given frequencyin a second given period after lapse of the first given period; in thecase where the step motor is rotationally driven by turning the secondand third switch elements on in accordance with the drive pulse, thecontrol means renders the third and sixth switch elements on andcontrols the on/off operation of the fourth switch element at a givenfrequency in the first given period immediately after the supply of thedrive pulse is finished, and renders the fourth switch element and thefifth switch element on in the second given period and controls theon/off operation of the third switch element at a given frequency; andthe detection means detects the presence/absence of the rotation of thestep motor on the basis of the comparison result of the voltagegenerated between the first detection element and the coil with thethreshold voltage when the fifth switch element is turned on, anddetects the presence/absence of the rotation of the step motor on thebasis of the comparison result of the voltage generated between thesecond detection element and the coil with the threshold voltage whenthe sixth switch element is turned on.
 2. A step motor control deviceaccording to claim 1, comprising: wherein the first, third, fifth, andsixth switch elements are made up of n-channel MOS transistors, and thesecond and fourth switch elements are made up of p-channel MOStransistors.
 3. A step motor control device according to claim 1,comprising: wherein the first and second detection elements are made upof resistors.
 4. An electronic timepiece comprising: a step motor thatrotates time hands; and a step motor control device that rotationallycontrols the step motor; wherein the step motor control device accordingto claim 1 is used as the step motor control device.